This invention relates to a controlling method for a grinding process.
In a grinding process, the speed ratio K.sub.v (workpiece surface speed/grinding wheel surface speed) and infeed amount per one workpiece revolution .DELTA. (infeed speed per minute/workpiece revolution per minute) have influence on grinding accuracy and efficiency. For obtaining both high grinding accuracy and high grinding efficiency, it is advantageous that rough grinding is performed under a condition in which the infeed amount .DELTA. is higher so that the ground surface of the workpiece is rather rough but good metal removal with high grinding ability is maintained so as to improve roundness and cylindricity of the workpiece, and that fine grinding is performed in a condition in which the infeed amount .DELTA. is lower so that grinding efficiency is rather poor but surface roughness of the workpiece is improved.
Further, revolution speeds of the workpiece and the grinding wheel, and infeed speed should be controlled to keep optimum K.sub.v and .DELTA..
In conventional grinding methods, revolution speeds of the workpiece and the grinding wheel, and infeed speed in rough or fine grinding step are respectively kept constant. Accordingly, the speed ratio K.sub.v is approximately constant and is not always suitable for rough grinding or fine grinding. Good surface roughness of the workpiece cannot be attained, in the prior art, without long time spark-out after fine grinding, in the spark-out metal removal rate diminishing as time passes, because the revolution speed of the workpiece in fine grinding is the same as that in rough grinding and is not suitable for improving surface roughness of the workpiece. Moreover, this surface roughness improving method with longer spark-out cannot effect constant quality on the workpiece surface as the grinding ability of the wheel or other factors sometimes changes the surface roughness.
The grinding wheel becomes smaller in the diameter after several dressings, shifting K.sub.v and .DELTA. to unsuitable values during rough and fine grinding which deteriorates grinding accuracy and efficiency.